The obvious point is that roofs have been built unnecessarily strong for decades.

Unnecessarily strong? 2kW of solar weighs about the same as one roofer.

If your roof can't hold up solar, it also can't hold up the people that need to work on it.

Because they can carry solar panels?

Roofs have to handle several tons of wind pressure, snow, people walking on them and so on. They can handle solar panels no problem - which is why it's such a good idea to put solar panels on them.